A partnership backed by Facebook, Amazon.com, Comcast and other major technology firms on Thursday established a $250 million fund to invest in startups that hope to capitalize on the growing reach of social networking.

The "S Fund" will be led by powerhouse Silicon Valley venture capital firm Kleiner Perkins Caufield & Byers, an early investor in Internet companies such as Amazon, AOL and Google.

The fund's backers are betting that the success of Facebook, which has more than 500 million members worldwide, is only the start of the next wave of "incredible and disruptive innovation," Kleiner Perkins partner John Doerr said.

So the investors want "to find and fund and accelerate the success of these new kinds of social entrepreneurs," Doerr said during a news conference hosted by Facebook.

Bezos also said he wants to find startups that will use his company's platform of cloud computing services, called Amazon Web Services.

"These social apps do tend to be very viral, and when they hit, they hit fast and they can grow violently," Bezos said. "That really does play to the strengths of Amazon Web Services."

Zuckerberg said the fund will help entrepreneurs who are trying to build social applications and services "from the ground up."

"The opportunity is there in the next five years or so to pick any industry and reimagine it in the social Web," he said.

The fund's first $5 million investment went to CafeBots Inc., a Palo Alto startup that is working on a "friend relationship management" platform to help consumers make better use of their social network.

The startup, the brainchild of three Stanford University graduates, hasn't released its product and is still in stealth mode.

CafeBots co-founder Michael Munie, 28, said that in addition to the money, inclusion in the fund gives his startup access to the entrepreneurial expertise of Kleiner Perkins, Facebook and the other investing companies.

As examples of the kind of "social Web" firms that could be funded, Kleiner Perkins trotted out representatives of several companies it previously invested in, including Flipboard Inc., which earlier this year launched a popular iPad app that creates a personalized magazine-style display of Facebook, Twitter and other news media feeds.